This invention relates to circuits for generating reference voltages. More particularly, the invention relates to a reference voltage generator (RVG) circuit whose output voltage varies inversely with its supply voltage. For the purposes of this invention, two voltages Va and Vb will be said to vary inversely if they can be related by the equation Vb=C-M Va where C is a constant and M is a positive constant.
Many electronic circuits make use of reference voltage generators in order to maintain a desired operating state. In most cases, the RVG's output voltage is required to remain essentially constant, independent of its supply voltage, but other RVGs having different relationships between the supply voltage and the output voltage are also possible.
RVGs whose output voltages vary inversely with supply voltage have some very useful applications. For example, the performance of many circuits depends critically on the supply voltage. Increasing the supply voltage has the undesirable effect of increasing the power consumed by the circuit, but coupled with this increased power dissipation is the desirable effect of increasing the speed of the circuit. Thus, in some voltage-controlled devices, it is desirable to increase or decrease the voltage supplying the device as the main supply voltage decreases or increases respectively. In this way, the variation of power dissipation in the device due to supply voltage fluctuations is minimized, and an optimum operating power level is maintained.
In view of the foregoing, it is an object of this invention to provide an RVG circuit whose output voltage decreases as the supply voltage increases, and whose output voltage increases as the supply voltage decreases.